1. Technical Field
The present invention relates to a measuring unit and a measuring method that are capable of measuring a physical quantity, such as temperature or humidity, a measuring data management apparatus and a measuring data management method that are capable of managing the measuring unit.
2. Description of the Related Art
Recently, in a variety of industrial fields including production, sale, physical distribution and inventory control, there has been developed a measuring system incorporating measuring units each having an appropriate sensor to measure a physical quantity, such as temperature, humidity, atmosphere or volume of air, so as to periodically supply results of the measurement to an managing apparatus, such as a personal computer and concentrically monitor the environments of areas.
The measuring system of the foregoing type records the physical quantity that the sensor measures, for example, the temperature, in a predetermined portion together with the date and time of the measurement. Recorded data will be used in a variety of purposes, for example, visualizing the temperature change by a graph, or detecting a cause of the temperature change in accordance with the date and time when the change is found. Therefore, the measuring system is required to obtain and record at least the time of the measurement in addition to the measurement data obtained by measuring the physical quantity such as the temperature.
In order to record the measurement time when data has been measured, a system containing a clock function such as a real time clock (RTC) system is required. In a measurement system having measuring units each disposed at a measuring position and using measurement data stored therein for a predetermined period of time the measuring unit to be disposed each position must be provided with the clock function. However, providing the clock function for each of the measuring units may raise the manufacturing cost excessively. What are worse, the size of the measuring unit will be unavoidably increased and the electric power consumption will be enlarged. When a plurality of measuring units are disposed at the respective measuring positions to measure the respective temperature thereof, each of the clock function provided for the measuring units has to be synchronized with each other at least periodically. As a matter of course, a system of the described above can be constituted. However, this may cause the measuring system to be further expensive and complicated. As the communication between the measuring unit and a central managing unit has to be performed frequently for such synchronization, there arises another problem of increased power consumption. Employing a clock system exhibiting an excellent accuracy and free from excessive variation may lower the frequency of synchronization. However, such a precise clock function will further raise the manufacturing cost. Therefore a measuring system described above cannot become readily available.
If the clock function is omitted from the measuring unit having a function of storing measurement data, the time of the measurement cannot be stored nor be used. In addition, a reservation function with which measurement start time is set and the measurement is automatically started at the set time cannot be provided for the measuring unit, resulting in inconvenient measuring unit for users.
Accordingly, an object of the present invention is to provide a measuring unit and/or a measuring method which are capable of finding the time of the measurement of individual measurement data without using clock function, and to provide a measuring data management apparatus and/or a measuring data management method which are capable of providing the time of the measurement of individual measurement data received from the measuring unit. Another object of the present invention is to provide a measuring unit and/or a measuring method which are capable of automatically starting a measuring operation at a measurement start time without a clock function, and to provide a measuring data management apparatus and/or measuring data management method which are capable of setting the measuring unit as described above.